Subjective Towers: Depth Relationships in Multilevel Subjective Contours

Salzman, Billie; Halpern, Diane F.

doi:10.2466/pms.1982.55.3f.1247

Cited by 7 publications

(3 citation statements)

References 12 publications

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“…Further examples to be explained are illusory surfaces that are slanted or bending in depth (Kanizsa 1974(Kanizsa , 1976, hierarchies of stacked illusory figures (Ehrenstein 1941(Ehrenstein , 1954Brigner and Gallagher 1974;Kanizsa 1974;Salzman and Halpern 1982), and three-dimensional objects such as the reversible illusory Necker cube (Piggins 1975;Bradley and Petry 1977). Nakayama and Shimojo's (1992) red cross embedded in a large white Ehrenstein figure also belongs here.…”

Section: Can We Bridge the Gap Between Levels Of Explanation?mentioning

confidence: 99%

Phenomena of Illusory Form: Can We Bridge the Gap between Levels of Explanation?

Spillmann

Dresp²

1995

Perception

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Abstract. The study of illusory brightness and contour phenomena has become an important tool in modern brain research. Gestalt, cognitive, neural, and computational approaches are reviewed and their explanatory powers are discussed in the light of empirical data. Two wellknown phenomena of illusory form are dealt with, the Ehrenstein illusion and the Kanizsa triangle. It is argued that the gap between the different levels of explanation, bottom-up versus top-down, creates scientific barriers which have all too often engendered unnecessary debate about who is right and who is wrong. In this review of the literature we favour an integrative approach to the question of how illusory form is derived from stimulus configurations which provide the visual system with seemingly incomplete information. The processes that can explain the emergence of these phenomena range from local feature detection to global strategies of perceptual organisation. These processes may be similar to those that help us restore partially occluded objects in everyday vision. To understand better the Ehrenstein and Kanizsa illusions, it is proposed that different levels of analysis and explanation are not mutually exclusive, but complementary. Theories of illusory contour and form perception must, therefore, take into account the underlying neurophysiological mechanisms and their possible interactions with cognitive and attentional processes.

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Section: Can We Bridge the Gap Between Levels Of Explanation?mentioning

confidence: 99%

Phenomena of Illusory Form: Can We Bridge the Gap between Levels of Explanation?

Spillmann

Dresp²

1995

Perception

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“…Subsequent studies using rating and magnitude scales (Bradley & Dumais, 1984;Halpem, 1981;Salzman & Halpern, 1982;Whitmore et al, 1976), matching (Coren & Porac, 1983), and nulling (Gregory & Harris, 1974;Whitmore et aI., 1976) verified that traditional edge-induced illusory figures (such as Kanizsa's figure) appear to hover in front of the inducers for most observers. There is some evidence that line-end illusory figures also appear stratified in depth, although to a lesser extent than do their edgeinduced counterparts (Coren & Porac, 1983).…”

Section: Characteristics Of Illusory Figuresmentioning

confidence: 99%

Illusory contours: Toward a neurally based perceptual theory

Lesher

1995

Psychon Bull Rev

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Although illusory contours were first described nearly a century ago, researchers have only recently begun to approach a consensus on the processes underlying their formation. Neurophysiological and psychophysical evidence indicate that neural mechanisms of the early visual cortex subserve illusory contour generation, although cognitive factors play important roles in determining the fmal percept. I summarize experiments concerning the determinants of illusory contour strength and form, concentrating on findings particularly relevant to modeling. After establishing arguments for the early generation of illusory contours, I provide an overview of formation theories, culminating with descriptions of neural models. The constraints that experimental data place on models are outlined, and neural models are evaluated with respect to these constraints. Throughout the review,I indicate where further experimental and modeling research are critical.Schumann introduced the first illusory contour, depicted in Figure 1a, in 1900, noting that a central "white rectangle with sharply defined contours appears, which objectively are not there." Schumann had discovered and noted two salient features of illusory figures: sharp edges in regions of homogeneous luminance, and a brightening within the figure. Perhaps because this stimulus failed to yield particularly convincing illusory contours, it was not until more than 50 years later that illusory contours became a topic for activeresearch. Although Ehrenstein (1941) demonstrated stimuli with salient illusory contours, it is remarkable that he failed to note their existence in the text of his article explicitly, commenting instead only on illusory brightening effects. Kanizsa's (1955) stunning figures, examples of which are depicted in Figures Iband 1c, produced extremely sharp, salient contours along with obvious brightening, initiating a wave of research.Although there have been a number ofexcellent illusory contour review papers Meyer & Petry, 1987;Parks, 1984), research advances in the psychophysical, neurophysiological, and modeling domains have been more than sufficient to mandate a new summary ofthe literature. Inthis review, I will not only present more recent data, but also employ an approach to the summaries that is markedly different from those previously taken. At the time of the earlier reviews, determination of the locus of formation of illusory contours was the central issue in illusory contour research, a fact reflected in the structure of the review papers. Experimental results were presented primarily in the historical context of supporting or refut-I would like to thank Ennio Mmgolla of Boston University for generously providing many helpful comments and suggestions during the development ofthis review.

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“…According to this position, subjective contours are perceived when portions of the stimulus display activate neural feature detectors, brightness contrast mechanisms, and/or spatial frequency analyzers (e.g., Day & Jory, 1980 ;Smith & Over, 1979) . Multivariate explanations combining depth cues, closure, and brightness contrast have also been proposed (Halpern, 1981;Halpern, Salzman, Harrison, & Widaman, 1983;Salzman & Halpern, 1982). For a review of the literature, see .…”

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confidence: 99%